nostyle.css

*{
    margin:0;
    padding:0;
    box-sizing:border-box;
}

:root{
    --bgcol:#37474F;
    --mcol0:#29B6F6;
    --mcol1:#2196F3;
    --mcol2:#1976D2;
    --txtcol0:#90A4AE;
    --txtcol1:#607D8B;
    --whitecol:#ECEFF1;
    --darkcol:#263238;
}


body{
    display:flex;
    flex-direction:column;
    align-items:center;
    padding-top:15vh;
    background: url('number.jpeg');
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    background-attachment: fixed;
}

#puzzle_container{
    position: relative;
    width: 50vh;
    height:50vh;
    background-color:var(--darkcol);
    border-radius:8px;
    border:1px solid var(--mcol0);
    box-shadow:0px 8px 0px var(--mcol0);
}

.puzzle_block{
    position:absolute;
    left:0;
    top:0;
    width:33.4%;
    height:33.4%;
    background-color:var(--txtcol1);
    color:var(--whitecol);
    font-size:10vh;
    font-weight:bold;
    text-align:center;
    padding-top:3%;
    cursor: pointer;
    user-select:none;
    transition:left 0.3s,top 0.3s;
}

/*difficulty container*/
#difficulty_container{
    display:flex;
    flex-direction:row;
    width:50vh;
    height:10vh;
    background-color:var(--darkcol);
    border-radius:8px;
    margin-top:22px;
}
.difficulty_button a{
    flex-grow:1;
    background-color:inherit;
    text-decoration: none;
    justify-content: center;
    align-items: center;
    color:var(--mcol2);
    text-align:center;
    font-size:3vh;
    font-weight:bold;
    padding-top:5%;
    margin:4px;
    cursor: pointer;
    transition:font-size 0.3s;
}
.difficulty_button a:hover{
    opacity:0.8;
    font-size:3.5vh;
}